Perthes’ disease versus sickle cell disease hip (18 Oct 2014)
[Rapid Response to Perthes’ disease by Peter Kannu & Andrew Howard
(Published 23 Sept 2014) British Medical Journal – Practice Easily Missed?]
The instructive article  of Peter Kannu and Andrew Howard (Oct 4, p 32) has presenting clinical
features that can equally apply to children with sickle cell disease whose omission in differential
diagnosis does not help busy Residents and House Physicians in hospitals anywhere in the world.
RADIOLOGICAL DIFFERENTIATION: PERTHES’ VERSUS SICKLE CELL DISEASE HIP
While clinical presentation – the limp with the physical signs elicited – is identical in Perthes’
and sickle cell disease hip in children the radiological features help in differentiation [2 page
239]. The latter hip differentiation “from Calve-Legg- Perthes’ disease is not difficult” 
especially when “the significant differences in age of onset, degree and site of epiphyseal
involvement and changes in the femoral metaphyses are considered” [4 5]. Like in Perthes’ there was
no hip involvement in 157 consecutive children with sickle cell disease aged 4 and below [2 page
239], but between 5 to 9 years of age there was 1 case in 201 consecutive sickle cell disease
patients (0.5%) and between 10 to 14 years we had 7 (4%) of 177 consecutive patients . Therefore
below the age of 15 years we in Ghana found 8 cases of avascular/aseptic femoral head necrosis in
200 consecutive sickle cell disease patients (2.5%) observed by one clinician (myself). The article
of Kannu and Howard  states: “The annual incidence of Perthes’ disease among children under 15
ranges from 0.2 to 19.1 per 100,000” which, while quoting the paper of Perry and colleagues on the
“racial and geographic factors on the incidence of Legg-Calve-Perthes disease” , failed to
comment that these so-called “racial factors” could be haemoglobinopathic.
DEFINITION OF SICKLE CELL DISEASE
Sickle cell disease is defined as possession of two beta-globin gene defects at least one of which
is the sickle cell gene , therefore the phenotypes constituting sickle cell disease are ‘SS’
known as sickle cell anaemia, ‘SC’ known as sickle cell haemoglobin C disease, ‘Sβ-Thal’ which is
sickle cell beta-Thalassaemia, ‘SF-HEREDITARY’ for sickle cell Hereditary Persistence of Foetal
Haemoglobin which 4 phenotypes comprised the commonest sickle cell diseases seen in Ghana. More
‘SC’ phenotype (6.6% of 603 consecutive patients of all
ages) than ‘SS’ (2’8 % of 600) suffered hip necrosis, but no disease phenotype is exempt 
ANYWHERE IN THE WORLD
Sickle cell disease occurs in significant measure in White people in Greece, Turkey, Sicily, and in
the Middle East, India, and in their descendants in the diaspora [2, pages 76-82]. Canada where
this article originates  has a good representation of these Mediterranean populations  as
well as Blacks and though the authors, as part of their investigations carried out for Perthes’
disease mention “a full blood count” there is need to remind Residents and House Physicians
anywhere in the world that haemoglobin electrophoresis must always be counted among the tests to be
carried out in any tentative clinical diagnosis of Perthes’ disease.
FORGETTING PAST PUBLICATIONS?
One Editor of a prestigious international medical publication once wrote asking me to limit my
references to articles published after the year 2000 AD. I wrote back to point out that clinical
signs were/are clinical signs and doctors needed reminding of their significance in any generation.
As part of their treatment regime Peter Kannu and Andrew Howard list “encouraging swimming” among
exercises to be recommended in Perthes’ disease. Well, fifty years ago bar 4 months I named in
Lancet swimming among the 17 commonest precipitating causes of sickle cell crisis . Mistake
sickle cell disease for Perthes’ disease and this advice to encourage swimming would be misplaced.
Fortunately, Obisesan and Bohrer  knew how to diagnose Perthes’ disease in Black children in
West Africa 42 years ago. Should the present authors have mentioned this? Or were they dismissing
anything published before AD 2000 as being of little significance? Just two out of their 13
references are before the 21st Century. The increasing habit of starting articles with a clinical
dimension thus: “We did a MEDSEARCH going back 25 years” is neither academic nor helpful, because
quite significant clinical material may be missed. In 1972 I discovered and described in The Lancet
a new physical sign in sickle cell disease, to the extent of quantifying its incidence in the
different sickle cell disease phenotypes, the peripheral mental nerve neuropathy of sickle cell
crisis  – what came to be known on ward rounds as the “kanumblll sign”. Twenty-five years later
Sally Davies and L Oni published in the BMJ a comprehensive article on Sickle Cell Disease 
limiting their references to cover the previous 25 years, thereby (but not deliberately) omitting a
vital physical sign (numb lower lip) that could have drawn the attention of any doctor or nurse to
the fact that the person they were confronted with had sickle cell disease.
Competing interests: None declared
Felix I D Konotey-Ahulu MD(Lond) FRCP(Lond) DTMH(L’pool) Kwqegyir
Aggrey Distinguished Professor of Human Genetics University of Cape Coast, Ghana and Consultant
Physician Genetic Counsellor in Sickle Cell and Other Haemoglobinopathies, 9 Harley Street Ltd,
Phoenix Hospital Group, London W1G 9AL (E-mail firstname.lastname@example.org Web: www.sicklecell.md)
1 Kannu P, Howard A. Perthes’ disease. BMJ 2014; 349:g5584 (doi:1136/bmj.g5584)
2 Konotey-Ahulu FID. The Sickle Cell Disease Patient: Natural History from a
Clinico-epidemiological study of the first 1550 patients of Korle Bu Hospital Sickle Cell Clinic.
The Macmillan Press Ltd, London 1991 & 1992 and T-A’D Co Watford, 1996.
3 Golding JSR. The bone changes in sickle cell anaemia. Ann Roy Col Surg Eng 1956; 19: 296-315.
4 Barton CJ, Cockshott WP. Bone changes in Haemoglobin SC disease. Am J Roentgen Rad Ther Nuc Med
1962; 88: 523-532.
5 Obisesan AA, Bohrer SP. Perthes’ disease in Nigerians. Ghana Medical Journal 1972; 11: 298-302.
6 Perry DC, Machin DM, Pope D, Bruce CE, Dangerfield P, Platt MJ, et al. Racial and geographic
factors in incidence of Legg-Calve-Perthes’ disease: a systematic review. Am J Epidemiol 2012; 175:
7 Ringelhann B, Konotey-Ahulu FID. Hemoglobinopathies & Thalassemias in Mediterranean areas and in
West Africa: historical and other perspectives 1910- 1997 – A Century Review. Atti del’Accademia
della Science di Ferrara 1998; 74: 267-307.
8 Konotey-Ahulu FID. Sicklaemic Human Hygrometers. Lancet 1965; 1: 1003-
9 Konotey-Ahulu FID. Mental nerve neuropathy: a complication of sickle cell crisis. Lancet 1972; 2:
388 [The so-called kanumblll sign (Konotey-Ahulu Numb Lower Lip Lancet sign)]
10 Davies Sally C, Oni L. Management of patients with sickle cell disease. BMJ
1997; 315: 656-660.