Desiderosmia: a manifestation of iron deficiency in pregnancy

Abstract

A pregnant woman in her 20s presented with an excessive desire to smell a specific household cleaning product. She was found to have severe iron deficiency anaemia and her symptoms resolved following intravenous iron supplementation. She described symptoms of fatigue, shortness of breath and olfactory cravings. The specific scent could not be replicated with other smells and the woman had to significantly modify her lifestyle to accommodate the excessive desire. She had a similar experience during her prior pregnancy which resolved after the correction of severe iron deficiency anaemia. This unique symptom has been described as desiderosmia: iron deficiency manifesting as olfactory cravings. This underappreciated but useful symptom is defined as a separate entity to pica, as there is an absence of desire to ingest the product. Desiderosmia can harm mother and baby through inhalation of potentially harmful fumes; hence, women who describe this symptom should be assessed for iron deficiency anaemia.

Background

Desiderosmia is defined as the excessive desire to smell certain odours without the need to eat, taste or lick, and is associated with iron deficiency anaemia.^{1 2} Few cases have been recorded in medical literature, describing the symptom as an excessive desire to smell a specific scent that improves after iron supplementation. Most self-reported cases in online forums and medical literature describe the craving for smells as a benign and embarrassing phenomenon in pregnancy.¹ This symptom has been investigated in comparison with the consumption of non-nutritive substances, pica.² Pica, however, is a distinctively separate behaviour involving repeated eating or desire to eat substances not fit as food, and olfactory desires are not considered to be pica behaviour.² The prevalence of pica is higher in pregnant women and in young children, with common non-foods such as dirt, clay, soap, ice and others.^{3 4} Cases of toxicity, malnutrition and lead poisoning due to pica have been reported in pregnancy, and hence a potential for similar toxic effects of noxious smells may occur in those with desiderosmia.⁵ This case report describes an unusual manifestation of olfactory cravings associated with iron deficiency that resolved after each iron replacement within the patient’s pregnancy. Current literature describes cases in non-pregnant populations; however, this report can help associate pregnancy-related cravings and iron deficiency anaemia. Additionally, this report can raise awareness of a symptom that may otherwise be overlooked.

Case presentation

A healthy 29-year-old, gravida 2 para 1 pregnant woman presented with an excessive olfactory craving during both of her pregnancies, without any desire to consume the substance. The cravings would occur during the third trimester of both of her pregnancies but resolved after iron infusions, significantly improving her quality of life. Iron deficiency was diagnosed during both pregnancies at 28 weeks as seen in table 1.

Table 1.

Iron levels in both pregnancies

	Olfactory craving	Haemoglobin (g/L)	Mean Corpuscular Volume (MCV) (fL)	Ferritin (μg/L)	Treatment
First pregnancy (>20 weeks)	Lemon cleaning product	97	74	<6	Iron carboxymaltose (1000 mg)
Intrapartum	None
Second pregnancy (>20 weeks)	Lemon lime body wash	109	89	<6	Iron carboxymaltose (1000 mg)

During her first pregnancy, she described symptomatic iron deficiency anaemia with fatigue, shortness of breath and olfactory cravings of a specific brand of lemon-scented cleaning detergent. She did not disclose the desiderosmia during her pregnancy despite requiring inhalation episodes of up to five times a day. She has no past psychiatric history or prior eating disorders. She has no symptoms of sinonasal conditions and no medical comorbidities. She was taking oral iron tablets and vitamin D₃ supplementation throughout her pregnancy. No abnormal clinical examination findings were documented. In Australia, ferritin levels are often assessed at the first antenatal visit and again at 28 weeks, particularly if there are risk factors for iron deficiency. Twenty-eight-week investigations for the patient revealed a microcytic anaemia with low ferritin (table 1). Her olfactory cravings resolved after an intravenous iron infusion in her third trimester, only to reappear during her subsequent pregnancy. She described no symptoms of anaemia or olfactory symptoms between pregnancies. She developed symptoms of lethargy, shortness of breath and excessive smell cravings during the second trimester of her second pregnancy, instead with a specific brand of lemon-lime body wash, again requiring multiple deep inhalations throughout the day. Outside of pregnancy, she did not complete any further blood tests.

Her scent cravings resulted in multiple inhalation episodes a day. Each inhalation episode is composed of multiple deep sniffs near the nose. The desire for the scent was specific to brand and type of cleaning product; no substitute was found that achieved similar satisfaction. The strong desire caused the patient to purchase multiple bottles to scatter throughout her house and to always carry bottles of the product with her. In retrospect, this was her main complaint during her pregnancies. She described the craving as an ‘addiction’, with a strong need to inhale the scent. There was no reported increase in sensitisation of general smells or reported adversity to other scents. There was no desire to consume the product or any excessive desire to consume any item (food or non-food). There were no dietary changes or any associated desire for other lemon-flavoured foods or smells. The symptoms were perceived as worse during her second pregnancy, where she had to excuse herself from social interactions and work to satisfy her craving. The disruption in quality of life led to her disclosure of this unique symptom to her obstetrician in her second pregnancy.

Differential diagnosis

Her main risk factor for iron deficiency anaemia was her pregnancy. She did not have any existing conditions, bleeding, vegetarian diet or history of malabsorption. On examination, she displayed pallor, shortness of breath and fatigue, but no palpitations, chest pain or neurological signs. She had no signs of malnutrition and was otherwise examined normally. Other than routine antenatal blood tests, further blood investigations such as a haemoglobin (Hb) electrophoresis excluded other causes of microcytic anaemia, concurrent haemoglobinopathies or familial haematological conditions. In the absence of neurological symptoms or seizure-like activity, no imaging was completed for frontal lobe seizures or stroke. Blood tests confirmed recurrence of iron deficiency (table 1) during her second pregnancy.

The working hypothesis for this symptom is desiderosmia associated with iron deficiency anaemia. After an iron infusion in both pregnancies, her symptoms improved, diminishing olfactory cravings from greater than five long episodes lasting a few minutes per day to three cravings over the span of 2 weeks and eventually completely resolving. She is now postpartum and has not reported any symptoms of desiderosmia.

Treatment

Her treatment of this incidental symptom was an iron infusion.

Outcome and follow-up

Currently, the patient has experienced no recurrence of desiderosmia in her postpartum course and continues to take oral iron supplements.

Discussion

The prevalence of anaemia in pregnancy in Australia is estimated to be up to 25% and can be higher in Aboriginal and Torres Strait Islander women.⁶ Iron deficiency is associated with poor gestational weight gain, foetal growth restriction, preterm delivery, increased risks of birth complications and depression during pregnancy. This effect continues into the postnatal period, where the mother can have impaired breast feeding and the newborn can have behavioural and cognitive disorders.⁶ Ferritin testing in unselected populations is not widely practised. The Department of Health in Australia recommends testing for serum ferritin if the Hb concentration is low for gestational stage at first visit (<110 g/L), 28 weeks (<105 g/L) and 36 weeks if symptomatic.⁷ Other indications for testing ferritin in Australia include women from areas of high prevalence of iron deficiency such as Aboriginal and Torres Strait Islander women, immigrants and adolescents. Women with a history of anaemia, postpartum haemorrhage, malabsorption syndromes and dietary restrictions are also often considered indications to consider testing ferritin. In the UK, anaemia is defined as Hb levels of <110 g/L in the first trimester, <105 g/L in the second and third trimesters, and <100 g/L in the postpartum period,⁸ although the WHO defines anaemia as <110 g/L at any stage of pregnancy.⁹ Recent studies in Europe suggest a greater drop in Hb levels is often seen between the first and third trimesters; hence, a higher than previously used Hb reference of <120 g/L in the first trimester should prompt investigation for iron deficiency.^{10 11} The patient in this reported case meets the criteria of iron deficiency anaemia in her first and second pregnancies, as seen in table 1.

Pregnancy causes a twofold to threefold increase in requirements of iron for the fetus and production of certain enzymes during the antenatal period.^{12 13} Physiological demand for iron increases by about 1 g during pregnancy and can reach 6–7 mg/day in the second half of pregnancy to reach its peak in the third trimester.^{6 13} Iron levels are therefore often tested during antenatal care and treated for both symptomatic relief and to build iron stores for potential blood loss during birth. Even with adequate iron stores at conception, serum ferritin will progressively fall to 50% prepregnancy levels due to haemodilution and mobilisation of iron. Hence, iron deficiency and consequent supplementation throughout the antenatal period is regularly needed.^6–8

Although research into the relationship between low ferritin and olfactory function in animals has been completed, the same has not been well tested in humans. In studies with rats, it is suggested that iron is a cofactor that controls behavioural olfactory function by participating in signalling through inhibitory pathways, and that iron has a key role in the synthesis of neurons involved in inhibition of odourant signals.¹⁴ In studies with piglets, the olfactory bulb was significantly different in size in piglets with severe iron deficiency, indicating the role of iron in other mechanisms.¹⁵ The role of iron in behavioural or sensory symptoms, such as pica, is not well understood, but other symptoms of increased tactile chewing and hearing loss have been reported with iron deficiency.^{16 17}

Pica has been extensively studied in pregnancy due to potential effects of ingestion of non-edible items leading to gastrointestinal issues, malnutrition, smaller neonatal head circumference and lead poisoning.^18–20 Desiderosmia in this case report is unlikely to lead to poor outcomes as household products are generally benign; however, if the craving was for a noxious scent, it could cause more harm. Previously reported cases of desiderosmia include a case of craving the scent of exhaust fumes, resulting in the commencement of smoking cigarettes to satisfy the craving.² Currently, there is no verified measured index to severity of this symptom in relation to severity of iron deficiency; however, the additional altered olfactory function may decrease appetite and affect nutrition, further highlighting the importance of recognising the symptom.²¹ Hence, history taking of specific cravings may be useful as it is often not disclosed openly due to embarrassment and fear of effects on pregnancy, and fear of yielding or not yielding to the compulsion.²²

Patient’s perspective.

During my first pregnancy, when I realised I was getting this ‘smell craving’ for lemon soap, I was only game enough to tell my husband because it was pretty embarrassing telling people that I loved smell of soap so much that I’d sniff it over 10 times a day. I didn't have an obstetrician either so I didn't have someone I could really confide in to tell this to. I resorted to Google and realised there were others similar to me in terms of weird cravings during pregnancy but not many.

During my second pregnancy when my craving was lemon and lime bicarb soap, I thought it was time to tell my obstetrician. Luckily I got one the second time round. It was embarrassing telling him I loved to sniff (strong sniff) bicarb multiple times a day. Not something I had told anyone except my husband the second time round either.

In my first pregnancy, it felt like I needed a ‘fix’ from time to time. It was a strong urge to smell it. There were other smells but I had one each pregnancy that were my weapons of choice. It was scary thinking I am inhaling toxic chemicals to a unborn child but the urge to get a fix was strong from time to time. I’d had a bottle of soap in my work drawer to smell from time to time. It wasn't a pleasant feeling to have. At times I felt like I was a drug/chemical addict.

I was iron deficient both pregnancies so I wasn't surprised that it could've been related to iron deficiency. Aside from naturally feeling tired during pregnancy, I never felt like I was so fatigued I couldn't get out of bed or extremely lethargic. There were no other symptoms relating to anaemia that really debilitated me.

I had my iron infusion at 38 weeks with my first pregnancy and at 35 weeks with my second. With my first pregnancy, I wasn’t really able to tell whether the iron infusion had made a difference to my symptoms, simply because I had it so late into the pregnancy to be able to notice a difference in symptoms before my daughter was born.

During my second pregnancy, I did start to see my ‘smell cravings’ reduce in urge after my infusion. Not instantly but maybe a week or so later.

One thing I wish I’d done earlier is definitely tell an obstetrician or a regular trusting doctor. I wished I wasn’t embarassed to open up and tell them my weird cravings from the beginning.

Learning points.

• Iron deficiency in often considered when a patient presents with pica, fatigue and lethargy.

• This case report demonstrates that iron deficiency should be considered if a pregnant woman describes desiderosmia.

• Women should be encouraged to discuss unusual symptoms and behavioural changes in pregnancy as they may indicate underlying medical conditions such as iron deficiency anaemia.

• Investigation and treatment of iron deficiency can help women deal with this embarrassing and potentially harmful behaviour.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s).